Space utilization on a Data Domain system is primarily affected by:
The size and compressibility of the backup data.
The retention period specified n the backup software.
High levels of compression result when backing up datasets with many duplicates and retaining them for long periods of time.
It is important to keep the Data Domain system less than 85% full. Filesystem Cleaning and other operations will be faster and more efficient when the system has enough available disk to perform these important tasks. Regularly keeping the system above 85% utilization can lead to fragmentation (file locality) issues, which will negatively impact performance of all operations, particularly cleaning and recovery attempts (if the system gets completely full).
Data ingest rate can also be affected if Cleaning time increases such that it starts to overlap with backup processes.
Additionally, seemingly minor changes in backup configurations, a shift in local compression efficiency, reduction in de-duplication rate, replication lag, retention policy change, or simply a cleaning run that is aborted can very easily cause the utilization to spike.
Most of these events are part of normal operation, and these utilization spikes will occur periodically.
However, if the system is nearly full (over 85%), there may not be adequate free space to absorb the spike until the condition resolves itself through normal operation (cleaning runs, replication catches up, etc).
If the system becomes completely full, it will automatically be locked into a read-only mode in order to protect existing data and no further backups can occur.
If recovery is possible, it will require special procedures that are very time-consuming (including deletion of some files to free up space). If the system can be returned to normal operation, GC (cleaning) will need to be run, and due to the full state of the system, this cleaning will take substantially longer than normal, measured in terms of days, and can even exceed a week.
These problems are easily avoided by maintaining a cleaning and utilization policy that keeps the system at no more than 85% full.
If the CPU utilization shows 80% or greater, or if the disk utilization is 60% or greater for an extended period of time, the Data Domain system s likely to run out of disk capacity or is the CPU processing maximum. Check that there s no cleaning or disk reconstruction in progress.
You can check cleaning and disk reconstruction n the State section of the system show performance report.